1. Field of Invention
This invention relates to an exercise apparatus. More particularly, this invention relates to a sit-up exercise apparatus.
2. Description of Related Art
There have been strong sales of exercise equipment in recent years, especially exercise equipment related to performing sit-up exercises. Most conventional exercise equipment of this type includes a seat, a seatback, a sliding wheel, and a spring. The seat is pivotally connected to the seatback. The sliding wheel is located at the backside of the seatback, is abutted against the ground, and undergoes rotation in this state contacting the ground. The spring is connected between the seat and the seatback. The spring provides a replacing force for replacing the seatback back to its original position.
During operation, the aforementioned sliding wheel of the exercise equipment undergoes rotation on the ground, as described above, and may also experience some sliding on the ground. As a result of such sliding, the path of pivotal displacement of the seatback relative to the seat will not be consistently located on a single vertical plane. Therefore, there is structural instability with such a configuration, ultimately resulting in a potentially dangerous situation. In addition, the aforementioned replacing force as well as the exercise resistance force is provided by the spring connected between the seat and the seatback. One consequence of this is that the exercise resistance will be monotonous and unchanging, minimizing the effect of training the muscles.
Moreover, because the sliding wheel is abutted against the ground, as described above, the maximum reclining angle of the seatback will be limited (i.e, angles larger than 80 degrees are typically not possible). Hence, the ability to perform back stretching exercises will be limited, as will the level of exercise intensity.